This invention relates to a gas bag restraing device.
Known gas bag restraining devices comprise a gas bag module which has a gas bag with a front wall which an occupant to be restrained can impact upon in a case of restraint, the front wall having a depression which is produced in that a center portion of the front wall is attached to the module and is prevented from free movement, preferably from any movement, when the gas bag is inflated, the gas bag restraining device further comprising a module cover closing a ring-shaped outlet opening of the gas bag module, the module cover having a central hole which is covered by a cap which is stationary during an opening process.
Such a gas bag restraining device is known from DE 197 49 914 A1. This device has a gas bag cover which in the region of the edge of the central hole is firmly attached to the module, to be more precise to a rigid guiding sleeve, and also remains attached thereto when the cover is opened. The module cover has two ring-shaped flap portions, one ring being disposed radially inside the other ring and both rings being formed by segments adjoining each other in peripheral direction. The cover tears between the adjoining rings, the segments of the inner ring swiveling towards outside and the segments of the outer ring inwards and towards each other. Then, the segments of the inner ring are only retained at the gas bag module by means of the guiding sleeve. Opening the cover should possibly always be effected with little and exactly predeterminable force. In the known restraining device, however, this is hardly possible.
The invention provides a gas bag restraining device in which the cover can be opened by the gas bag with a small and relatively exactly predeterminable force.
This is achieved in a gas bag restraining device which comprises a gas bag module which has a gas bag with a front wall upon which an occupant to be restrained can impact in a case of restraint. The front wall has a depression which is produced in that a center portion of the front wall is attached to the module and is prevented from free movement, preferably from any movement, when the gas bag is inflated. The gas bag restraining device further comprises a module cover closing a ring-shaped outlet opening of the gas bag module. The module cover has a central hole which is covered by a cap which is stationary during opening of said gas bag module. The module cover has an edge defining the central hole and opens, preferably tears, towards outside starting from the edge. A holding connection is provided between the edge and the cap which is released when said module is opened. Preferably, the holding connection is a positive, i.e. form fitting, connection. When the module cover bursts, it does not partly remain in the region of the cap, but owing to a releasable holding connection it is able to tear radially from the inside towards outside and radially swings from the inside towards outside which is possible with distinctly less effort than in the case of a closed ring-shaped tear line. The opening behavior of the module cover can thus be improved.
Preferably, the cap makes a tongue-and-groove joint with the edge, so that on the one hand, the edge of the cover cannot be seen from the outside. On the other hand, the cover cannot be levered open in the region of the edge, as the edge is not accessible.
In accordance with an alternative embodiment, the edge is clamped between an underside of the cap and a part of the module to which the cap is attached. This part of the module is, for instance, the gas generator or a diffuser surrounding the gas generator.
The module cover may consist of opposing flap portions having a parting joint where these flap portions are positively connected with each other. Thus, the flap portions are separate portions which already before opening of the cover are two distinct parts, but which owing to the positive connection cannot easily be opened from the outside.
Another embodiment makes provision that the module cover has an end wall and a side wall, the end wall being clamped at the transition to the side wall. Such clamping may at the same time serve as a hinge and thus as a swivel axis for the flap portions of the end wall. Moreover, this embodiment is not only restricted to a ring-shaped gas bag and a cover closing a ring-shaped outlet opening, but the clamping principle is rather applicable to conventional module covers as well.